Going... Going... Gone?

Pinpointing extinction is a tricky business.

Cover Story

December 03, 2004|By David Kohn | David Kohn,SUN STAFF

What ever happened to the White Warty Back? The Lined Pocketbook? The Coosa Elk Toe?

That's what Arthur Bogan wants to know. For 18 years, he's been looking for these creatures - all species of freshwater mussel that were once plentiful in Southeastern rivers and streams. Bogan has looked all over, without success, and suspects the species are extinct, victims of pollution, and dams that choke the bivalves with silt.

But looking for mussels is tricky work. Bogan sometimes snorkels, or uses a glass-bottomed bucket. The water is often too murky to see, so he has to work blind. "You're neck deep in water, running your hands across the bottom," says Bogan, a mussel specialist at the North Carolina State Museum of Natural History. "It's all done by feel."

The upshot: It's hard to know for sure whether there are any Pocketbooks or Elk Toes still hiding in the watery depths.

Bogan's dilemma is by no means unusual. Establishing that a species has gone extinct is a muddy, inexact process, rife with unanswered questions and ambiguity. Even worse, ecologists say, thousands of creatures are disappearing - or have already vanished - without anyone even noticing. With more and more creatures becoming endangered, conservationists say, the questions will only multiply.

Just this week, the U.S. Fish and Wildlife Service announced that a Hawaiian bird called the po'ouli was likely gone forever after the last one in captivity died. But two po'ouli known to live in a remote Maui rain forest may still be alive, so the final judgment is on hold. Ecologists have launched a search to find the pair, who were last seen a year ago.

"It's extremely difficult to prove that something has disappeared from the face of the earth. There has to be no reasonable doubt that the last individual has died," says Cambridge University biologist Jonathan Bailey.

An expert on endangered primates, Bailey wrote the extinction section for the Conservation International Red List, the world's most authoritative catalog of endangered and extinct flora and fauna. Published last month, the latest survey reported that more than 15,000 species are threatened with extinction - an increase of more than 3,000 since last year.

"When things are very rare, they're very hard to find," says Simon Stuart, an ecologist with Conservation International. For the past three years, Stuart has been directing a mammoth survey of the planet's 5,743 amphibian species. Despite its scope, the study, which appeared in October, left many questions unanswered. Investigators say that 109 species seem to have gone extinct since 1980, but could gather enough definitive evidence for only nine of them.

Frogs and mussels aren't the only elusive creatures. Even much larger organisms can be hard to count. Take sperm whales, which can grow to 60 feet long and weigh as much as 90,000 pounds. Until recently, most scientists estimated that 2 million swam the oceans. But a new survey, using a different calculation method, came up with a figure of just 360,000.

Both estimates rely heavily on sightings, a frustratingly imprecise measure, says ocean ecologist Vassili Papastavrou of the International Federation for Animal Welfare: "You're only seeing a tiny part of the ocean, and only the surface. There are all sorts of errors inherent in any estimate." He says the true number of sperm whales remains a mystery, and he worries that the animals may be more endangered than now thought.

One problem is that criteria for determining extinction vary widely. Groups that track endangered organisms - Conservation International, the U.S. Fish and Wildlife Service, Birdlife International and many others - all have their own standards.

Generally, the rules come down to the fact that no one has seen a particular plant or animal over a given period of time. But the guidelines are not uniform. Until 1996, Conservation International would declare an animal extinct only if it hadn't been seen for 50 years. But it dropped the rule after deciding that some extinctions could be verified more quickly.

Back from the `dead'

In some cases, a 50-year wait isn't long enough - animals can turn up decades after decades of supposed nonexistence. These creatures are known as "Lazarus" species because they seem to rise from the dead. Among the most famous is the Lord Howe Stick Insect.

Known as the "land lobster," the creature is 10 inches long, with a body as thick as a hot dog. It originally lived on Lord Howe Island off Australia, and supposedly disappeared in 1924, annihilated by non-native rats who escaped from visiting ships.